A pathologist has a central role in the diagnostic part of the care cycle. When a tissue sample is taken from a patient during a biopsy, it is usually the pathologist who makes a final diagnosis as to the nature and gravity of the disease (mostly cancer related), by microscopic inspection of the tissue and cells from the biopsy.
A microscope slide containing material from a biopsy is typically prepared in several steps as follows. First, the material is usually placed in formalin for fixation and subsequently processed into a paraffin block from which thin (˜5 μm) slices are cut. One of these slices is then placed on a microscope glass substrate after which one or more staining agents are applied such that relevant cell or tissue parts are visible with a microscope. Finally a matching fluid/fixative is added to the slice and a thin (˜170 μm) microscope cover slip is placed on top of the tissue such that the slice is completely sealed. This enables long time (>10 years) storage of the slide including the slice. Often it is also compulsory to store the paraffin blocks for at least ten years as well.
Although pathology is currently an analogue profession there is a strong drive to move towards digital pathology in order to improve diagnostic efficiency and quality. Digital pathology refers to digitization of the slide in the lab, to storing the resulting images on a server to allow easy access by the pathologist from his or her workstation, and to sharing the clinically relevant information with peers and other clinicians. Adoption of digital pathology would result in the pathologist handling the slides no longer himself, but instead to work with the digital images and other clinical information for making his or her diagnosis.
Using a suitable dissection technique, for example, microdissection by laser (laser microdissection), one or several small samples can be cut out of a tissue slice and be subjected to further molecular testing such as DNA genotyping or RNA transcript profiling. The preparation of the tissue slides is quite analogous to the case of pathology tissue slides, with the difference that now no cover slip is placed on the tissue in order to enable extraction and collection of the selected tissue samples. Histological examination is done by microscopic inspection leading to a selection of one or several areas of interest. Often this selection is made by the pathologist and marked on the back side of the slide. An operator can then use a focused laser beam for cutting along a line that separates the area of interest and the surrounding tissue. The separated tissue is then collected in a collection basket using an adhesive tape or by catapulting it with a defocused beam, after which the collected tissue is processed further. Currently, laser microdissection systems are mainly used in research labs.
A problem standing in the way of more widespread adoption of laser microdissection in the general pathology practice is the fact that current microdissection systems are not matched with the existing pathology workflow. It is currently not possible to do laser microdissection on samples that are used for normal diagnosis due to the presence of the cover slip on the sample. These normal slides should not be damaged during processing. Furthermore, the pathologist currently has to handle the physical slide to indicate which area should be selected, which leads to more slides to be transported to and from the lab. This mismatch in workflow might further increase with the introduction of digital pathology since the pathologist will then no longer handle any physical slides. There is thus a need for a novel system that integrates microdissection into a digital pathology workflow.
It is an object of the invention to facilitate the combined steps of selecting a region of interest in biological material and extracting material from the region of interest. It is another object of the invention to facilitate controlling a workflow involving at least two slices cut from, e.g., the same paraffin block.
These objects are achieved by the features of the independent claims. Further specifications and preferred embodiments are outlined in the dependent claims.